Oni provides two complementary types of gameplay:
- "Brutal unarmed combat"
- "Furious gunplay"
Oni's gunplay is fairly straightforward in comparison to other video games. There are various weapons (listed below) with varying behaviors, reload times, ammo clip sizes, and accuracy. Oni is notable in that Konoko can only carry one weapon at a time, holstered or not (two if using the weapon-shifting cheat), in contrast to most action games, where ten or twelve weapons might be carried by the player at one time.
The tech specs for each weapon are found here.
Reload judiciously. Reload only when it's safe to do so to avoid being interrupted (which can cause you to lose a clip) or disarmed. When forced to enter melee combat while out of ammo, holster your weapon, or fight with it if you don't have time to do so. You can still pull off all your old moves with a one-handed pistol if it's out of ammo. A weapon which requires two hands to wield will change some of your moves, such as the Devil Spin Kick and the standard punch, but fighting like that is still perfectly feasible until you've earned enough breathing room to reload or holster your weapon.
Use the Campbell Equalizer Mk4 with precision. This weapon can be used for single shots or fired on full auto, but the incredible recoil means it's almost impossible to hit an enemy at mid- or long-range on auto. Also, enemies will evade a steady stream of bullets, so the only effective way to use this weapon is for single, careful shots -- unless the enemy is just outside of melee range, at which point automatic fire will be fairly deadly.
Wait for the right range with the Hughes Black Adder SMG. "Deadly at close range, but only useful for suppression fire beyond 6 meters." -- The in-game instructions are succinct and accurate. If you just love to tangle with enemies in melee combat, this weapon is second only to the VDG in terms of close-range usefulness. Virtually any throw can be followed up by emptying half of the weapon's clip into your opponent; this is especially true for the Backbreaker, Lariat, or Stepping Disarm, and can be used on nearby enemies other than the one you're throwing with the standard forward+punch throw or the Suplex when behind an opponent (you can fire, but not aim, while throwing).
The SML3 Plasma Rifle is a sniper's friend. This is the most accurate long-range weapon besides the Mercury Bow, and much easier to come by. Make sure to account for the blast's slow initial velocity but quick mid-flight acceleration when attacking moving targets. When on the receiving end of plasma fire, you should have little to no trouble avoiding enemies' pitiful attempts to hit you. Just dash toward your opponent in a zig-zag fashion like an alligator's on your tail.
Use the Phase Stream Projector to hold one foe at your mercy. The stream loses it dangerousness when hitting walls, you can't use it you shoot around corners. The weapon isn't a huge damage dealer, but it does stun its target. Since the enemy will be mostly unable to fight back as long as you hold down the trigger, a clear target is likely as good as dead as long as you have enough charge left to close the deal. There are better tactics to take out even a pesky melee opponent, but when dealing with an armed foe, this is one of the best ways to defend yourself from his shots.
Use the SBG Man-Portable Mortar for tactical explosives. Do not use at close range! But incredibly useful when you have a good distance between yourself and your enemy. When facing enemies wielding a Superball Gun themselves, take them out at long range if possible. If not, close the distance as quickly as you can; if they shoot at you when you're nearby, the explosion will send them flying as well, effectively disarming them and allowing you to turn the tables as you pick up their weapon.
- Delayed detonation: Hold down the trigger until you want the main mortar to explode. You can hit larger groups by releasing the trigger when mortar is in mid-air. Hold down the trigger until the mortar comes to a stop on the ground to place a "land mine" that goes off when the trigger is released.
- Ricochet: The mortar can bounce off walls and obstacles, so you can surprise an enemy by shooting around a corner.
Turn the tables in melee with the Van de Graaff (VDG) Pistol. This weapon is simply the best weapon you could possibly hope to have in a melee battle. It stuns opponents in a small arc in front of you. Don't miss; its rate of fire is extremely low. The moment your opponent(s) is/are stunned, go for the most brutal offense you can (like a Backbreaker) or run for cover if that's a wiser decision based on the odds. (Note that stunned enemies, though they can't react to you, can still see you, so running behind a small obstacle while they're stunned is useless since they'll just follow you once they're no longer dazed.) When you're facing a VDG, especially against multiple opponents, it can be a nightmare if you don't have a forcefield. But if you jump just before you are hit with the weapon, you'll simply be knocked out of the air rather than stunned, and can get to your feet much more quickly than if you had been stunned. Does 1HP damage.
Keep it long-range with the Scram Cannon. Missile warheads are inactive at close range (but will do still damage*). For best results, give swarms lots of space to home in on their targets. When you're the target, evade by hiding behind enemies or obstacles. (You can also match the speed of the warheads by dashing.) A quick flip and/or slide should be sufficient to dodge the missiles as well once you've gotten the hang of their maneuverability and homing; for example, try to lure them upwards with a jump, then slide below them as soon as you land.
(*)Kill a weak enemy by running into them and shooting them point-blank.
The Mercury Bow - a rare and valuable weapon. Kills all but the strongest enemies with one shot. Two shots uses up an ammo clip, so make sure it's the most useful weapon you can get for the upcoming situation before spending your ammo on it (in some situations against multiple enemies, a Superball Gun might be preferable). Although the bow takes a very long time to re-freeze before it can fire again, if you made your first shot, then you probably finished off the enemy. If not, it might be best to drop the weapon before melee ensues.
The Screaming Cell shows that Konoko's not the only living weapon in Oni. The Screaming Cell Cannon fires a capsule which explodes a second or so later, doing no damage but releasing a creature that flies around and drains the life energy of anything nearby for a short while. It actively hunts down a random target within range other than the person who fired the weapon, but since it drains life from anything within range, it can easily harm the SCC's wielder if (s)he gets too close. Use it either as a long-range weapon to take out distant, unalerted enemies with a single attack, or use it in close-range combat by dancing around your opponent and letting your hungry friend do the work while you focus simply on dodging. The creature flies slowly enough, and the SCC's rate of fire is slow enough, that enemies using this against you are pretty much doomed if you just tackle them with a running throw or the like and confiscate their weapon.
Become a human tank with the Wave Motion Cannon. Something of a novelty weapon. Only available (without cheats) in the Vago Bio Lab level (Ch. 3). If you don't have the time to pull off a shot, drop it before it becomes a burden holding you down in combat. Konoko can only walk while wielding it.
- Primary fire mode: Don't use the energy beam at short distances; it takes too long to charge the shot. If you can keep the beam on an enemy for the full duration of the shot, it may well kill him in one shot.
- Secondary fire mode: Fires a frag grenade that sends enemies flying. Does much less damage than primary fire mode, but buys you a little time to use the beam again.
The melee combat in Oni was designed from the start as a crux of the gameplay. Great effort was undertaken to create a balanced system of strikes, combos, special attacks, blocks, and dodges, inspired by fighting games such as the Street Fighter series. Attacks are initiated with only two keys, one for punching and one for kicking (also, the left mouse button is punch, and the right button is kick), but complexity is introduced by varying the attacks based on Konoko's movement and with combos such as p-p-k (short for "punch-punch-kick", which yields the powerful Sledgehammer Heel). Blocking simply requires facing the opponent and not pressing any keys, but some attacks break through blocks enough to cause a stun effect and/or do chipping damage, and some are so powerful that they cannot be blocked. Jumping attacks and low attacks (such as leg sweeps) also add challenge to melee combat. One must be crouching to block a low attack, thus requiring fast reflexes; in addition, overhead attacks such as jump attacks and certain other moves can only be blocked while standing. The more advanced enemies are noticeably better at fighting than the ones encountered early on.
When Konoko is in a tight situation or is surrounded, she can use an escape move such as a cartwheel, or call on an omnidirectional attack such as kicking when coming out of a crouch (Devil Spin Kick) to clear some room.
Block before attacking. Oni does not reward button-mashing when fighting advanced opponents. In fact, any enemy can surprise you with a quick jab between your own attacks if you do not pay attention to defense. Wait for an opening before punching or kicking, such as when an enemy is not facing you or when they have just finished an attack. Learn enemy combos, so you don't try to counterattack in the middle of a combo and let the next attack through your defense. However, this doesn't mean you should just turtle while waiting for the perfect opportunity to counter your opponent; not only can some attacks do chipping damage even if you block them, but some enemies will just throw you.
"Both the high road and the low road have hidden rewards." Get the high ground by keeping your opponent knocked down at all times. Useful methods to do this include the crouch+punch move, the crouching sweep kick, an attack in any direction but forward, or any jump attack. A prone opponent is a predictable opponent, as there are only so many ways he can get to his feet. If they try to get up with an attack, it'll usually be in the direction of their feet, so stay near the head of a fallen foe if you want to wait for him to get up before beating him to the ground again. When fighting on stairs, on the other hand, the low ground is preferable: you can block low attacks while standing, high attacks will generally miss you, all your attacks must be blocked low (allowing you to hit with an overhead like a jump attack) and a prone opponent can be hit by a full Triple Hit Haymaker combo without any possibility of retaliation.
Keep it fresh. Enemies adapt to your moves quickly. Don't expect to pull off the same move twice in a row. Keep asking yourself, "What haven't I tried yet?" Also, alternate between high and low attacks. In fact, several such attacks chain well into others, such as a high punch --> low punch/crouch+punch combo, or a forward kick --> slide combo. Of course, there are some moves which are always effective simply due to their unblockability; a properly aimed Twister Kick, for example, should hit your opponent at an angle from which he cannot block, so even the best AIs in Oni can't do a thing.
Be stealthy. Enemies cannot hear Konoko when she is crouch-walking or crouch-running. This allows you to sneak up behind them to get in a couple pre-emptive hits. You can also go for a Backbreaker (forward-kick while standing closely behind enemy), which may end the fight before it begins.
Enemies are the best projectiles you can have. Throwing enemies into each other is an extremely effective way to hold off multiple attackers. Make sure you know which throws are best in which situations for that purpose. The forward+kick throw, for example, is great for knocking down people behind you, as opposed to the forward+punch throw's effectiveness in the opposite direction.
Know when to retreat. Facing even two enemies at once can make a fight much more difficult. Omnidirectional attacks like Rising Fury and Devil Spin Kick are useful, but hard to pull off consistently when under attack. A quick cartwheel or side-roll will do wonders in avoiding enemy offensives. When truly overwhelmed, running away will draw your pursuing enemies out behind you in a line, at which point you can turn and attack the closest one, then run away again.
Bring a gun to a fistfight. If you knock an opponent down, you probably have time for a leg sweep or jump-flip to add damage, but you could also pull out your weapon and squeeze off a couple shots before they get up. Make sure you holster it before resuming the fight, however, or you will quickly be disarmed.
Know thyself, know thine enemy. Sun Tzu's wisdom applies to small-scale battles as well. As important as knowing every move in Konoko's repertoire is knowing the details of your opponents' movesets as well. Get a feel for the ranges of different enemies' attacks versus your own; the best way to deal with an opponent's attack is not to be there. For example, several throws in Oni have rather lethal range, such as the Striker's standard throw, the Tanker's forward+kick "throw" (the your-face-meets-my-knee move), et cetera, so make sure you don't let an enemy get within his throw range unless one or both of you is attacking at the time. Remember that enemies love to throw you as you're doing escape moves, which sometimes block attacks but never evade throws, so make sure to watch out for that.
Do your own stunts. The default combos are quite useful, but learn which attacks chain well into others so that you can make up some of your own combos as well. Think about what you want to set up (probably a Backbreaker), think about how best to set it up (have your opponent prone so that, as he gets up, you can hit him with a jab --> Backbreaker combo), and think about how to get to that setup (a forward+punch throw, a slide, or a crouch+forward+punch trip). Now experiment with what moves will combo into that one. Voila, you've got yourself a punch --> crouching punch --> crouch+forward+punch --> dash --> slide combo that will end up with your opponent flat on the ground and you behind him, ready to crush him the moment he gets to his feet. Oops, did I just give away one of my favorite combos? Meh. Get your own.